Do not use bundled libobjc on Darwin.
Refactor cmake scritps: introduce os.cmake, arch.cmake,
compiler.cmake, libobjc.cmake, luajit.cmake.

Remove the hack with building libobjc/luajit as a
dependency on cfg.

Do not specify -ggdb when compiling with clang.

Add -fno-objc-legacy-dispatch and -fobjc-nonfragile-abi
when compiling with CLang on Linux.

Remove -fgnu-runtime when compiling with gcc on Mac.

Many minor cleanups.

Conflicts:
	connector/perl/lib/MR/Tarantool/Box.pm
	connector/perl/t/03-box.t
	connector/perl/t/data/init.lua

Conflicts:
	connector/perl/t/03-box.t

Conflicts:
	connector/perl/t/03-box.t

libobjc2 has a notion of "small objects". The type
of a small object is detected by checking its address:
it should not be word-aligned.

When performing a custom memory allocation for Request,
make sure it's not a small object, by aligning it around
(void *) pointer (word) boundary.

object_dispose in libobjc2 runtime doesn't check whether
the passed in object is nil, so check for nil outside.

Add a makefile to libobjc.

See README in this patch for a description of the import
procedure.

Fix a typo in the code which would move the code
to the Objective C 2.0 runtime. Correctly check
for the size of area necessary to store the object (vs.
allocated area) to make a decision whether or not we
need to re-allocate.